Conventional surface protective layers and interlayer insulating layers for semiconductor devices can include a polyimide resin, which can have excellent heat resistance and electrical characteristics, and mechanical characteristics, among other properties.
Polyimide resins have recently been used in the form of a photosensitive polyimide precursor composition. This polyimide precursor composition can be coated on a semiconductor device, patterned by ultraviolet (UV) rays, developed, and heat imidized to easily form a surface protective layer, an interlayer insulating layer, and the like. Recently, semiconductor devices have become thinner and smaller but with increased chip integration.
A positive photosensitive polyimide precursor composition can include a polyimide precursor of polyamic acid, a photosensitive material of diazonaphthoquinone, and the like. However, the positive photosensitive polyimide precursor composition may not provide a desired pattern, because the carbonic acid of the polyamidic acid used therein can be too highly soluble in an alkali.
Unlike the positive photosensitive polyimide precursor composition, a region exposed to radiation should rapidly dissolve during development, while dissolution of a region which is not exposed to radiation should be suppressed in the patterning process. However, since conventional materials may not effectively suppress dissolution of an unexposed region and rapidly dissolve an exposed region, the coated layer can be thinner after development, even when more energy is used for patterning.
Japanese Patent Laid-Open Publication Pyeung 3-209478 discloses a photosensitive polyimide-based resin that can be developed in an alkali aqueous solution. Japanese Patent Publication Pyeung 11-044948 and Japanese Patent Laid-Open Publication Pyeung 11-65107 disclose a positive material prepared by combining a polyimide or a polyamide having a phenolic hydroxyl group with diazonaphthoquinone. However, this resin can result in poor optical transmission and may not form a pattern on a 10 micrometer or thicker layer. In addition, since the resin has a low molecular weight in terms of its development properties and is included in a smaller amount than diazonaphthoquinone as a photoresist, there can be problems associated with its use, such as low concentration and strength deterioration of a layer.
In order to solve this problem, Japanese Patent Laid-Open Publication No. Pyeung 10-30739 discloses a material including a hydroxyl phenol group introduced through an ester bond instead of carbonic acid. However, this material may be insufficiently developed, which can cause problems such as reduced layer thickness and delamination of the resin from a substrate.
Japanese Patent Publication Soh 63-96162 discloses a material prepared by mixing a diazonaphthoquinone compound with a polybenzoxazole precursor. However, it can be difficult to obtain a desired pattern after development using this material, since layer thickness can decrease in the unexposed region.
A polybenzoxazole precursor with a higher molecular weight can be used to reduce the decrease in layer thickness. Increasing the molecular weight of the polybenzoxazole precursor, however, may cause development residue, and thus can deteriorate resolution and extend development time.
Japanese Patent Laid-Open Publication No. Pyeung 9-302221 and Japanese Patent Laid-Open Publication No. 2000-292913 disclose a method of suppressing loss of layer thickness in an unexposed region by adding a particular phenol compound to a polybenzoxazole precursor composition. These methods, however, may not sufficiently suppress the decrease in layer thickness. Accordingly, there is still a need for a material and method which can prevent or minimize the generation of residue and also can effectively suppress loss of layer thickness.
In addition, there is a need for a dissolution-controlling agent, since phenol is decomposed or negatively reacts at a high temperature during thermal curing, or forms micropores in a layer during high temperature evaporation, which can significantly damage mechanical properties of the cured layer. It also should be free from sensitivity deterioration and be solution-storage stable depending on its amount.